FAIRFEILD — NorthBay Healthcare, using the stage of a grand opening for its $20 million Green Valley Health Plaza, announced plans to begin major construction projects on its two hospital campuses in Fairfield and Vacaville that will total an additional $180 million.

NorthBay Healthcare has joined the network of Minnesota-based UnitedHealthCare, which will enable some 11,000 Solano County residents to be treated at NorthBay’s two hospitals and various clinics , the two companies announced.